您可以通过wpdb class:

$query =    "SELECT COUNT( DISTINCT meta_value )
            FROM $wpdb->postmeta
            WHERE meta_key = \'city\'";       
$unique_cities = $wpdb->get_var( $query );
echo \'Total number of cities: \' . $unique_cities;

您可以通过wpdb class:

$query =    "SELECT COUNT( DISTINCT meta_value )
            FROM $wpdb->postmeta
            WHERE meta_key = \'city\'";       
$unique_cities = $wpdb->get_var( $query );
echo \'Total number of cities: \' . $unique_cities;